The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without payment of any royalties thereon or therefor.
1. Field of the Invention
The present invention pertains to warheads and more particularly to warheads capable of penetrating into sand or concrete covered, deeply buried, bunkers without prematurely initiating the warheads"" explosive charge, for instance, exploding before reaching living and storage spaces within the bunker.
2. Description of the Related Art Warheads serve many functions related to the attack of area targets. One particular function that is important to attacking an area is the destruction of hard and buried targets such as control centers bunkers buried in sand or covered with concrete as well as targets such as runways in order to immobilize air forces.
Many concepts have been developed to address these types of targets. For example, U.S. Pat. No. 4,967,666 discloses a warhead that uses a forward hollow charge in order to create a passageway for an internal, follow-up projectile to be fired into fortified or armored targets. U.S. Pat. No. 5,780,766 discloses a similar type of xe2x80x9ctwo-stagexe2x80x9d device comprising an armor piercing hollow charge that clears a region for the missile to reach its final destination, where upon impact, a post-firing fragmentation explosive charge is released due to inertia. U.S. Pat. No. 5,526,752 discloses a projectile that includes multiple warheads separated by casing with independent detonators wherein the warheads are detonated sequentially in order to penetrate the target. U.S. Pat. No. 5,939,662 discloses a missile warhead comprising a tungsten ballast to provide high warhead sectional pressure upon impact. Finally, U.S. Pat. No. 6,283,036 discloses a variable output warhead comprising several compartments separated by a shock-absorbing shield, each filled with explosive material wherein the shield prevents sympathetic detonation from one compartment to another. Depending upon the target, a specific number of compartments can be selected for initiation.
While these and other designs have provided some success in attacking hardened and deeply buried targets, the inherent trade off between the ability of a warhead to penetrate to a target and the stresses that this penetration places upon the explosive fill within a warhead have proven problematic. Current penetrating warheads are designed so the explosive occupies a single, long and narrow compartment in order to achieve the highest practical sectional density. This design results in significant stresses being placed upon the explosive fill. Such stresses on the explosive fill often cause premature initiation, prior to the completion of the desired penetration, thereby causing failure of the mission. These stresses also cause the outer walls of the warhead to bulge, thereby increasing the tendency of the warhead to buckle under axial loads and rupture. One method of dealing with this latter problem in the past has been to increase the thickness of the outer walls of the warhead. However, when the explosive is finally detonated, a significant amount of the explosive energy is used in fragmenting these thicker outer walls, resulting in low velocity fragments and a weaker blast, i.e., reducing the lethality of the warhead. Therefore, a warhead with improved penetration and explosive potential at the target is necessary in order to more readily complete military critical missions.
The present invention comprises a warhead for penetrating hardened or buried targets, comprising a super-cavitating nose and a cellular structure for containing explosive material. The cellular structure comprises an outer wall and a plurality of discs that are axially spaced within the cellular structure to form separate cells. There is a central axis approximately through the center of the warhead wherein a load bearing support is located to provide structural support for the cellular structure. Within each cell the explosive material is divided. Finally, initiation means are present to begin the detonation of the explosives.
Accordingly, it is an object of this invention to provide a warhead that increases penetration into hardened or buried targets.
It is a further object of this invention to provide a warhead design that reduces stresses on the explosive material within the warhead while penetrating hardened or deeply buried targets.
It is a further object of this invention to provide for warheads in general, and penetrating warheads in particular, a structural design that is inherently stiff, i.e., resists buckling and deformation at the same or even reduced weight; that exploits the stresses generated within the explosive during penetration to stiffen the load bearing components of the structure even further; and that allows the use of thin outer walls, thus allow more of the explosive energy to be channeled in producing high velocity fragments and a strong blast.
A still further object of this invention is to integrate the different design elements of the warhead such that they all work in concert, enhancing each other""s role and performance.
This invention accomplishes these objectives and other needs related to warheads for hardened and buried targets by providing a warhead that employs a super-cavitating nose along with a cellular structural design that uses a reinforced central post as the main load-bearing component and subdivides the explosive cavity into shorter sections.
A super-cavitating nose, by definition, significantly deflects the flow past a projectile or structure travelling at high speed, away from its lateral boundaries, thus reducing the drag on the structure as well as other forces acting at the interface between the flow and the boundaries.
For example, if so equipped, a super-cavitating nose on a torpedo forces the water to flow off the edge of the nose with such speed and at such an angle that the water cannot wrap around the surface of the body of the torpedo. This allows the drag on the torpedo body to be significantly reduced because it is no longer in contact with the water, having a high density, but it is in contact with water vapor, having a low density. This allows the torpedo""s velocity to greatly increase due to the overall decrease in friction. The present invention uses a super-cavitating nose design in order to enhance penetration and travel of the warhead through sand, concrete or other impediments between the warhead and the target in a similar manner as that described above. Because the sand and rubble do not come in contact with the body of the warhead and therefore do not exert any forces on the outer walls, they can be made thinner in order to increase the resulting fragment velocity and blast.
The present invention also deviates from the traditional design of aerial (BLU) bombs utilizing thick outer walls and no internal structural support. Instead, the present invention uses a cellular warhead structure with a reinforced central post as the main load-bearing component. In addition to being inherently stiff, this structural design subdivides the explosive cavity into shorter sections. Because the stresses induced in the explosive material during penetration are proportional to the height of the explosive subjected to the deceleration, this reduces the stresses to which the explosive is subjected and the likelihood of premature initiation. Using a central post as the main load-bearing component also allows us to use thinner outer walls, which increases the fragments velocity and blast.